/* * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009 * The President and Fellows of Harvard College. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * This file is shared between libc and the kernel, so don't put anything * in here that won't work in both contexts. */ #ifdef _KERNEL #include <types.h> #include <lib.h> #else #include <stdint.h> #include <string.h> #endif /* * C standard function - copy a block of memory, handling overlapping * regions correctly. */ void * memmove(void *dst, const void *src, size_t len) { size_t i; /* * If the buffers don't overlap, it doesn't matter what direction * we copy in. If they do, it does, so just assume they always do. * We don't concern ourselves with the possibility that the region * to copy might roll over across the top of memory, because it's * not going to happen. * * If the destination is above the source, we have to copy * back to front to avoid overwriting the data we want to * copy. * * dest: dddddddd * src: ssssssss ^ * | ^ |___| * |___| * * If the destination is below the source, we have to copy * front to back. * * dest: dddddddd * src: ^ ssssssss * |___| ^ | * |___| */ if ((uintptr_t)dst < (uintptr_t)src) { /* * As author/maintainer of libc, take advantage of the * fact that we know memcpy copies forwards. */ return memcpy(dst, src, len); } /* * Copy by words in the common case. Look in memcpy.c for more * information. */ if ((uintptr_t)dst % sizeof(long) == 0 && (uintptr_t)src % sizeof(long) == 0 && len % sizeof(long) == 0) { long *d = dst; const long *s = src; /* * The reason we copy index i-1 and test i>0 is that * i is unsigned -- so testing i>=0 doesn't work. */ for (i=len/sizeof(long); i>0; i--) { d[i-1] = s[i-1]; } } else { char *d = dst; const char *s = src; for (i=len; i>0; i--) { d[i-1] = s[i-1]; } } return dst; }